Conventionally, an operating system (OS) and various application programs are stored in a storage device such as a hard disk drive (HDD) of respective computers so as to be executed in them. In contrast to this, recently a storage centric system is disclosed. That is, OS and various application programs stored in storage devices of separate computers are collected in a network type storage device (hereinafter, referred to as a storage device) and backup and virus scan are executed all at once. Each PC of this system uses a logically divided storage region (LU: Logical Unit) of the storage device instead of a local HDD.
A volume (a storage region recognized by the OS of the PC) allocated for a PC is uniquely determined by a combination of a target defined in a port of the storage device and an LU created on a disk of the storage device. In the port of the storage device, a plurality of targets are defined. The PC is connected to the allocated target and can use the LU mapped on the target as the local disk of the PC.
A method for allocating an LU of a storage device connected by a network for a computer is disclosed, for example, in JP-A-2001-350707, in which a virtual LU is defined on the PC. When an access to the virtual LU occurs, a storage allocation program on the PC collects evaluation data from the storage device, decides a usable LU, and registers it on the PC. Thus, the PC side can allocate the storage device or the LU.
It should be noted that as the storage device or the LU evaluation data, an IO delay time, an IO frequency, a backup frequency, presence/absence of volume dual write function, an empty volume (region where no LU is created) are disclosed.
Moreover, a method for allocating an LU of the storage device connected by a network for a computer is disclosed, for example, JP-A-2006-209294, in which a target to be allocated can be selected so as to make the port load equal.